The present invention relates to an N-(.alpha.-acyloxyethyl) compound, which belongs to a class of novel organic compounds not known in the prior art nor described in any literatures, and a simple and efficient method for the preparation thereof. The present invention has been completed on the basis of an unexpected discovery obtained in the course of the investigations undertaken by the inventors with an object to develop an efficient method for the preparation of N-vinyl compounds having usefulness as a reactive monomeric compound for the preparation of special polymeric compounds.
As is known, N-vinyl compounds in general have good polymerizability and high reactivity so that they are widely used as a class of industrially very important reactive monomers in the preparation of various kinds of specialty polymers and as an ingredient in ultraviolet-curable resin compositions.
For example, N-vinyl-2-pyrrolidone is used as a starting monomer in the preparation of polyvinyl pyrrolidones as a typical water-soluble polymer or as an ingredient in an ultraviolet-curable resin composition. Further, various kinds of N-vinyl amide compounds are now highlighted and under extensive investigations as a starting monomer for the preparation of a polymer to be useful as a cationic polymeric flocculant, for example, in the process of sewage disposal.
Various methods have been proposed heretofore for the preparation of these N-vinyl compounds. Taking N-vinyl-2-pyrrolidone mentioned above as an example, known methods for the preparation thereof include: (1) a method in which acetylene and 2-pyrrolidone are reacted under high pressure or in the presence of an alkali as a catalyst as disclosed in U.S. Pat. No. 2,806,847 and French Patent 1,340,350; (2) a method in which a vinyl ether or a vinyl carboxylate and 2-pyrrolidone are reacted in the presence of a mercury salt or a palladium compound as a catalyst as disclosed in Japanese Patent Publications 38-4882, 47-8302, 47-8303, 47-2083 and 47-2001; (3) a method in which N-(.alpha.-hydroxyethyl) pyrrolidone or an N-(.alpha.-alkoxyethyl) pyrrolidone is subjected to thermal decomposition as disclosed in French Patents 1,534,369 and 1,421,336; (4) a method in which N-(.beta.-hydroxyethyl) pyrrolidone or N-(.beta.-acetoxyethyl) pyrrolidone is subjected to thermal decomposition as disclosed in Japanese Patent Publication 48-44251 and USSR Patent 125,507; and so on.
Among the above described prior art methods, the first method has already been rendered to practice as an industrial process although this method is never so advantageous because the investment for the plant construction is high as a consequence of the high-pressure reaction along with a risk due to eventual explosion. The other prior art methods are also industrially not practicable because the yield of the desired products cannot be high enough unless the reaction is conducted under very severe reaction conditions if not to mention the expensiveness of some of the starting materials and the catalyst compounds.
In view of the above described problems and disadvantages in the prior art methods for the preparation of an N-vinyl compound, the inventors have conducted extensive investigations to develop a simple and efficient method for the synthetic preparation of the compound by conducting experiments through a widely different routes starting from a variety of known compounds as well as some novel compounds which are not known in the prior art but supposedly could be a promising intermediate material for the synthesis of an N-vinyl compound.